The move could broaden the recruiting pool for underwater duty, which like other branches of the armed services, faces a shortage of talented volunteers. And this could be one of the last gender barriers to fall in the Navy.

But critics, including top Navy brass, say the initiative would raise costs and increase the rigors of one of the world's most challenging work environments.

Women line up on both sides of the debate, with opposition surfacing in one group that, though quiet in public, carries considerable weight behind the scenes: wives of current submariners.

"The majority of wives and family members do not want women on submarines," says Tami Calhoun of Groton, Conn., an opponent of gender integration on subs and director of the Submarine Wives Club, a support group.

From the Pacific to the Atlantic, wives voice concerns ranging from adultery to stress and reduced morale.

Women have served on combat surface ships since 1994, and now make up 14 percent of the Navy's 370,000 personnel. But service aboard subs has remained closed to women, a policy Navy leaders want to maintain.

"The extreme conditions on submarines - submerged 24 hours a day for months at a time, in a crowded environment that affords almost no privacy - are a major factor that should drive submarine-personnel policy," the Navy stated in a 1995 review.

But in October, the Defense Advisory Committee on Women in the Services, a Pentagon panel that reviews issues facing female military personnel, recommended the Navy plan to integrate women onto future Virginia-class attack submarines, which begin deployment in 2004.

Integrating the subs would expand the talent pool, potentially easing a shortage of qualified recruits that has persisted despite pay incentives. It's also a question of equal opportunity, the Pentagon panel suggested, allowing "the assignment of the most highly qualified personnel regardless of gender."

Women sailors say they're interested and able. "I would jump at it," says Cristina Brittian, an enlisted deck seaman based in Norfolk, Va., who has repaired subs in dry dock and is training to become a sonar technician on a destroyer. "It would be an honor to serve on board a submarine."

Not so fast, say many submariners' wives. Their top objection is the prospect that mixed-gender service in such close quarters - and under extreme tensions - may invite promiscuity. Passageways on attack subs are so narrow that sailors have to turn sideways to pass one another, they say.

"I do not want my husband that close to some other female," says Shelli Brown of Harker Heights, Texas. "I love [my husband] and trust him, but it's the other one I don't trust."

Other concerns range from bathrooms and bunks to potential pregnancies. Aboard fast-attack submarines, two bathrooms - each with four toilets and two urinals - serve 100 crew members. Crew chiefs and officers use another three baths. Designating one bath for a small number of women could disadvantage scores of men, while making them unisex raises other problems.

Currently, some enlisted sailors must sleep on the same bunk in shifts, a practice known as "hot racking." If women get their own berthing area, more sailors may "need to start hot racking again," says Cheryl Morrissey of Ballston Spa, N.Y. "How is that for morale?"

A pregnancy could be "instant trouble," Mrs. Morrissey adds. "We risk giving away the location of the sub" to off-load a pregnant sailor.

In any case, the all-male fraternity would disintegrate, critics argue. "Just to keep themselves sane ... they have discussions and rituals that just couldn't be done around ... women they are working with," says Mrs. Calhoun. "You take these things away from them, then what do you have? A monotonous schedule [and] unhappy working conditions."

Not all submarine wives believe such concerns should be showstoppers.

"The fears are not well thought out," says Sonja Jones of Poulsbo, Wash., whose husband is an officer with experience on small and large subs.

Sailor Brittian, who is married to an enlisted submariner, echoes this: "Almost all of them have never served on board a combatant vessel.... Their concerns are often founded on hearsay."

She says it is difficult to imagine sailors having affairs on the job in this serious environment. Submariners tend to spend what little downtime there is just catching a few hours of sleep.

Pregnancies on board would be rare, both women argue. The Navy routinely screens women on surface ships for pregnancy prior to each deployment.

Ms. Jones says unisex showers and toilets have a long history, noting they were depicted in "M*A*S*H." She also suggests that bunk issues are manageable. Curtains are already used on each "rack" to guard privacy and block out light, and all submariners remain on call in jumpsuit uniforms when they sleep.

Similarly, Jones has few concerns about how integration would degrade morale. "I'm not sure these [male] rituals are what make a ship safe, or what make it run," she says. "So I think they can do without it."